The present invention relates to a roll for a rolling mill.
A conventional roll of this kind is disclosed for example in U.S. Pat. No. 4,599,770.
The conventional roll comprises, as shown in FIG. 1, a sleeve 3 fitted for example by shrink or expansion fit over a central barrel of a roll core 2 which in turn is rotatably supported at its opposite ends by bearings 1. The sleeve 3 has opposite ends each of which has an inner periphery in the form of a tapered surface 4 diverged toward the end of the core 2; that is, the diameter of the tapered surface 4 is gradually increased toward the end of the core 2 so that an annular space 5 is defined between the core 2 and the tapered surface 4. Piston rings 6 and 7 each having a tapered surface serving as a wedge surface are axially slidably fitted over the core 2 and within the space 5. The space 5 is liquid-tightly closed by a seal ring 8 so that a liquid-pressure chambers 9, 10 and 11 are respectively defined between the blind end of the space 5 and the ring 6, between the rings 6 and 7 and between the rings 7 and 8. The chambers 9, 10 and 11 are respectively communicated with liquid passages 12, 13 and 14 which in turn are formed in the core 2 and are communicated with exterior liquid-pressure source means (not shown). Supply of a liquid under pressure to or discharge of the liquid from the chambers 9, 10 and 11 causes the tapered piston rings 6 and 7 to be axially displaced to thereby be wedged or unwedged in the space 5. As a result, the outer shape of the sleeve 3 or of the roll can be varied.
Use of the rolls with such variable configurations as work rolls, intermediate rolls and/or backup rolls is advantageous in rolling of works with different widths and enables control of thickness distribution of works along their widths as needs demand.
The conventional roll, which comprises the sleeve 3 fitted over the rotatably supported core 2 by shrink or expansion fit, has the following problem. That is, when the rolling forces F are applied to the roll, the latter is deflected as indicated by FIG. 2. In this case, the inside and outside (the upper and lower surface in FIG. 2) distortions of the core 2 due to the deflection are different from each other; however, the inside and outside distortions of the sleeve 3 due to deflection are substantially the same so that the sleeve 3 is axially displaced or dislocated with respect to the core 2 as indicated by 15 in FIG. 2.
Once such axial displacement or dislocation 15 occurs between the roll core 2 and the sleeve 3, even when the rolling forces are removed, the roll remains deflected since the displacement or dislocation 15 cannot disappear because of high contact pressure having been applied between the core 2 and the sleeve 3 due to shrink or expansion fit.
The roll, which cannot be returned to its initial straight state and remains deflected, is eccentrically rotated, resulting in nonuniform distribution of thickness of works in their lengthwise direction.
In view of the above, a primary object of the present invention is to provide a roll for a rolling mill which can return its initial straight state when rolling forces are removed even if it has been deflected by application of the rolling forces.